JP6278147B1 - Mixed cement - Google Patents

Abstract

[Problem] To provide a mixed cement containing coal ash, maintaining the characteristics as an admixture of coal ash and having high short-term strength development. SOLUTION: The total amount of coal ash and Portland cement is 20 to 40% by mass of coal ash having a SiO2 content of 55 to 60% by mass and a SiO2 / Al2O3 mass ratio of 2.3 to 2.7. And 60 to 80% by mass of Portland cement, and 100 to 300 mg / kg of trialkanolamine having 3 linear alkanol groups having 3 or less carbon atoms. [Selection figure] None

Description

  The present invention relates to a mixed cement mixed with coal ash.

  With the increase in power generation at coal-fired power plants, the generation of coal ash is increasing. Most of the coal ash is industrial waste, but it is difficult to secure a disposal site for industrial waste, and environmental regulations are strengthened, so the effective use of coal ash is required. Coal ash discharged from thermal power plants is broadly divided into fly ash and clinker ash, and fly ash is collected by a dust collector out of coal ash generated when coal is burned at a coal thermal power plant. It means fine ash. Clinker ash is obtained by crushing massive coal ash that has fallen into the water tank at the bottom of the boiler in a red hot state with a crusher. About 90% of coal ash is fly ash.

  From the viewpoint of effective use of coal ash, fly ash cement using fly ash as a mixture is manufactured and sold. The quality of a part of fly ash used as an admixture for cement is defined in JIS A6201 “Fly Ash for Concrete”. In the present specification, coal ash refers to fly ash.

Coal ash contains pozzolans containing silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) as main components. Pozzolana in coal ash reacts slowly with calcium hydroxide (Ca (OH) ₂ ) produced by cement hydration reaction (Pozzolanic reaction) to produce hydrate, Contributes to strength development. On the other hand, in order to supplement the strength development of the short-term age of the cured product, as a strength enhancer, a composition containing a reaction product obtained by reacting glycerin and formaldehyde, or mannose, galactose, talose, ribose, and erythrose A composition containing a specific amount of one or more compounds selected from the group has been proposed (Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 2014-189417 Japanese Patent Laid-Open No. 2014-237577

  The mixed cement using coal ash as an admixture has almost no hydraulic property in the short-term age in the coal ash itself, so that the short-term strength development of the 3-day age is lowered. To supplement short-term strength development, even if a conventional strength enhancer is used, depending on the amount of components and coal ash contained in the coal ash used as an admixture, short-term strength development A sufficient improvement effect cannot be obtained.

  Therefore, an object of the present invention is to provide a mixed cement containing coal ash, maintaining the properties as an admixture of coal ash, and having high short-term strength development.

The present inventors have, as a result of intensive studies to achieve the object, among the pozzolanic contained in coal ash, silica and the content of (SiO _2), alumina _(Al 2 _{O 3)} to silica (SiO ₂ ) Mass ratio (SiO ₂ / Al ₂ O ₃ ), these mixed cements containing coal ash in a specific range maintain the properties of coal ash as an admixture, while exhibiting short-term strength development properties. The present inventors have found that a high mixed cement can be obtained and completed the present invention. That is, the present invention is as follows.

[1] Coal ash having a SiO ₂ content of 55 to 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3 to 2.7 with respect to the total amount of coal ash and Portland cement is 20 Mixed cement containing 100 to 300 mg / kg of trialkanolamine containing 3 to 40 straight-chain alkanol groups containing 3 to 40% by weight of Portland cement and 60 to 80% by weight of Portland cement.
[2] The mixed cement according to [1], wherein the trialkanolamine is triethanolamine.
[3] The mixed cement according to [1] or [2], wherein the total content of SiO ₂ and Al ₂ O ₃ in the coal ash is 70 to 82% by mass.
[4] The mixed cement according to any one of [1] to [3], wherein the content of Fe ₂ O ₃ in the coal ash is 5.0 to 8.0% by mass.
[5] The mass ratio of the amount of iron in the crystalline phase contained in the coal ash to the amount of iron in the coal ash (the amount of Fe in the crystalline phase / the amount of Fe in the coal ash) is 0.10 to 0.17. The mixed cement according to any one of claims [1] to [4].
[6] The mixed cement according to any one of [1] to [5], wherein the content of acid-insoluble residue (insol) in the coal ash is 75 to 87% by mass.
[7] The mixed cement according to any one of [1] to [6], wherein the coal ash has a Blaine specific surface area of 2500 to 4000 cm ² / g.
[8] The mixed cement according to any one of [1] to [7], including 25 to 35% by mass of the coal ash and 65 to 75% by mass of Portland cement.

  According to the present invention, it is possible to provide a mixed cement that includes coal ash and has high short-term strength development properties while maintaining the properties of the coal ash as an admixture.

The present invention will be described below.
In the embodiment of the present invention, the SiO ₂ content is 55 to 60% by mass and the mass ratio of SiO ₂ / Al ₂ O ₃ is 2.3 to 2.7 with respect to the total amount of coal ash and Portland cement. A mixed cement containing 20 to 40% by mass of coal ash and 60 to 80% by mass of Portland cement and 100 to 300 mg / kg of a trialkanolamine having three linear alkanol groups having 3 or less carbon atoms It is a composition.

[Coal ash]
Coal ash has a SiO ₂ content of 55 to 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3 to 2.7. The coal ash is preferably generated from a coal-fired power plant.
When coal ash is used as an admixture for cement, the mechanism is not clear, but the content of SiO ₂ , which is one of the main components of pozzolans, and the main components of pozzolans (SiO ₂ , Al ₂ O ₃ ) It was found that the mass ratio (SiO ₂ / Al ₂ O ₃ ) contributes to, for example, the short-term strength development of a 3-day age.
Pozzolana in coal ash reacts slowly with calcium hydroxide (Ca (OH) ₂ ) produced by cement hydration reaction (Pozzolanic reaction) to produce hydrate, It is known to contribute to strength development.
In the mixed cement of the present disclosure, the hydration reaction of Portland cement contained in the mixed cement is promoted by a chelating action of a trialkanolamine having three linear alkanol groups having 3 or less carbon atoms, and at a relatively early stage. Pozzolanic reaction between calcium hydroxide (Ca (OH) ₂ ) produced by hydration reaction of Portland cement and pozzolanic components (Al ₂ O ₃ , SiO ₂ ) in coal ash occurs, and short-term strength development is Presumed to improve. Further, when the cation (for example, calcium ion (Ca ²⁺ ) or aluminum ion (Al ³⁺ )) in Portland cement is masked by the chelating action of the trialkanolamine, the equilibrium state of the hydration reaction of the mixed cement is maintained. Therefore, it is presumed that the cation contained in the pozzolanic component (SiO ₂ , Al ₂ O ₃ ) in the coal ash is likely to react. The mixed cement of the present disclosure was accelerated in the hydration reaction of Portland cement at an early stage by the chelating action of the trialkanolamine, and was contained in the generated calcium hydroxide (Ca (OH) ₂ ) and coal ash. It is speculated that the pozzolanic reaction with pozzolanic components (Al ₂ O ₃ , SiO ₂ ) is also promoted at an early stage, which is considered to contribute to the improvement of the short-term strength development.
In the present specification, chemical components such as SiO ₂ , Al ₂ O ₃ , and Fe ₂ O ₃ in coal ash are values measured in accordance with JIS R5204 “Method for X-ray fluorescence analysis of cement”.

SiO ₂ content in the coal ash is 55 to 60 wt%, preferably 55.0 to 59.5 wt%, more preferably 55.0 to 59.0 wt%. If the SiO ₂ content in the coal ash is less than 55.0% by mass, the SiO ₂ content, which is one of the pozzolanic components contained in the coal ash, is too small, and the mixed cement containing the coal ash is desired long-term May not exhibit the strength development of When SiO ₂ content in the coal ash exceeds 60.0 wt%, since it is often SiO ₂ content in the coal ash, the content of relatively _Al 2 _{O 3} is reduced, _SiO 2 / Al The mass ratio of ₂ O ₃ exceeds 2.7. The content of SiO ₂ contained in coal ash has a correlation with the content of other components contained in coal ash, such as Al ₂ O ₃ , Fe ₂ O ₃ , CaO, and MgO contained in coal ash. Yes, when the SiO ₂ content in the coal ash increases, the content of other components tends to decrease relatively.

The mass ratio of SiO ₂ / Al ₂ O _{3 in} the coal ash is 2.3 to 2.7, preferably 2.30 to 2.65. When the mass ratio of SiO ₂ / Al ₂ O ₃ in coal ash exceeds 2.7, the content of silica (SiO ₂ ) in coal ash is large, and the content of alumina (Al ₂ O ₃ ) is high Even if calcium ions and aluminum ions in the mixed cement are masked by the chelating action of the trialkanolamine, the pozzolanic reaction is promoted at an early stage because there are few aluminum ions in the pozzolanic component of coal ash. Therefore, it becomes difficult to increase short-term strength development.

Total content of SiO ₂ and _Al 2 _{O 3} content in the coal ash, preferably 70 to 82 wt%, more preferably 72.0 to 82.0 wt%, more preferably 75.0 to 81.5 % By mass. When the total content of SiO ₂ and Al ₂ O ₃ in the coal ash is 70 to 82% by mass, Portland cement can be obtained by the chelating action of the trialkanolamine together with the mild pozzolanic reaction contributing to long-term strength development. If the cation in Portland cement is masked by the chelating action of the trialkanolamine and the equilibrium of the hydration reaction of the mixed cement is maintained, The cation contained in the pozzolanic component (SiO ₂ , Al ₂ O ₃ ) is likely to react, and the pozzolanic component (Al ₂ O _3, SiO ₂ ) contained in the coal ash at a relatively early stage is Portland cement water. pozzolanic reaction is promoted by reaction with the calcium hydroxide produced by hydration reaction (Ca (OH) _2), short It believed to contribute to the improvement of the strength development of.

The coal ash has an Fe ₂ O ₃ content of preferably 5.0 to 8.0% by mass, more preferably 5.1 to 7.9% by mass. And _Fe 2 _{O 3} content in the coal ash, but the mechanism is not clear contributes to short-term strength development, _Fe 2 _{O 3} content in the coal ash is 5.0-8.0 wt% , SiO ₂ content contained in coal ash and other components other than SiO ₂ contained in coal ash, such as Al ₂ O ₃ , Fe ₂ O ₃ , CaO, MgO, etc. in coal ash from _relations, the mass ratio of SiO 2 / _Al 2 _{O 3} tends to be 2.3 to _2.7, the mass ratio of SiO 2 / _Al 2 _{O 3} tends to become a suitable range contributes to the short-term strength development It is guessed.

The mass ratio (the amount of Fe in the crystalline phase / the amount of Fe in the coal ash) of the amount of iron in the crystalline phase (the amount of Fe in the crystalline phase) contained in the coal ash to the amount of iron in the coal ash (the amount of Fe in the coal ash) is: Preferably it is 0.10-0.17, More preferably, it is 0.110-0.170. The mass ratio of the amount of iron in the crystalline phase contained in the coal ash to the amount of iron in the coal ash (the amount of Fe in the crystalline phase / the amount of Fe in the coal ash) is the amount of crystalline phase contained in the coal ash and the amorphous phase It becomes an index representing the mass ratio of the quantity. In the present specification, the amount of Fe in the crystalline phase is determined by the method for measuring the crystalline phase and the amorphous phase (mass%) in coal ash described in the examples described later, and includes the total amount including unburned carbon. The amount of crystalline phase Fe calculated taking the amorphous phase amount G _total (% by mass) into consideration. In the present specification, “the amount of crystalline phase Fe calculated taking into account the _total amount of amorphous phase G _total (% by mass) including unburned carbon” is also referred to as “the amount of Fe in the crystalline phase”.
When the amount of Fe in the crystalline phase / the amount of Fe in the coal ash is 0.10 to 0.17, the amount of iron in the crystalline phase is relatively small, in other words, the amount of the crystalline phase that does not contribute to the pozzolanic reaction in the coal ash. It is presumed that the amount of amorphous phase including alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) contributing to the pozzolanic reaction is relatively small and relatively large. When the amount of Fe in the crystal phase / the amount of Fe in the coal ash exceeds 0.17, it is presumed that the content of the crystal phase in the coal ash increases, and an amorphous phase that is relatively easy to contribute to the pozzolanic reaction Less. The crystalline phases in the coal ash, such as quartz or cristobalite _(SiO 2), mullite _{(3Al 2} O 3 · 2SiO ₂ or _{2Al 2 O 3 · SiO 2)} , hematite _{(Fe 2 O} 3), magnetite _(Fe 3 O ₄ ) and the like.
If the mass ratio of the amount of Fe in the crystal phase / the amount of Fe in the coal ash representing the index of the amount of crystalline phase and the amount of amorphous phase in the coal ash is 0.17 or less, the amount of crystal phase in the coal ash is small, The amount of the amorphous phase is relatively increased, and the hydration reaction of Portland cement is promoted at a relatively early stage by the chelating action of the trialkanolamine to produce calcium hydroxide (Ca (OH) ₂ ). It is presumed that a pozzolanic reaction between calcium hydroxide (Ca (OH) ₂ ) and a pozzolanic component (Al ₂ O ₃ , SiO ₂ ) contained in the amorphous phase occurs and short-term strength development is improved. Furthermore, when the cations in the Portland cement are masked by the chelating action of the trialkanolamine, the pozzolanic component (SiO ₂ , Al ₂ O in the coal ash is used to maintain the equilibrium state of the hydration reaction of the mixed cement. ₃ ) The cations contained in ₃ ) are likely to react, and the reactivity of the pozzolanic reaction, which reacts relatively slowly, is promoted even at an early stage, which is considered to contribute to the improvement of short-term strength development. The mass ratio of Fe amount in the crystalline phase / Fe amount in the coal ash, which indicates the index of the crystalline phase and the amorphous phase of the coal ash, the smaller the numerical value, the less the crystalline phase in the coal ash and the more the amorphous phase. In other words, the pozzolanic component (Al ₂ O ₃ , SiO ₂ ) contained in the coal ash increases, and the pozzolanic reaction is likely to occur. Usually, the mass ratio of the amount of crystalline phase Fe in coal ash / the amount of Fe in coal ash is 0.10 or more.

The insoluble residue (insol) content of the coal ash is preferably 75 to 87% by mass, and more preferably 75.5 to 86.5% by mass. It is considered that the insoluble residue in the coal ash includes a crystalline phase and an amorphous phase (glass phase) constituting silicic acid and silicate. The mechanism by which the insoluble residue (insol) in the coal ash contributes to the short-term strength development is not clear, but if the insoluble residue (insol) in the coal ash is 75.0 to 87.0% by mass, The amorphous phase containing the pozzolanic component (Al ₂ O ₃ , SiO ₂ ) that contributes to the pozzolanic reaction contained in the coal ash becomes relatively large, the content of SiO _{2 in} the mixed cement, and the SiO ₂ / Al By including the coal ash in the preferred range and the trialkanolamine with a mass ratio of ₂ O ₃ , it was contained in the coal ash at a relatively early stage together with a mild pozzolanic reaction contributing to long-term strength development. pozzolan component _{(Al 2 O 3, SiO 2} ) is the pozzolanic reaction is promoted by reaction with the calcium hydroxide produced by hydration of portland cement (Ca _{(OH) 2),} short-term It is possible to increase the strength development.
In this specification, the insoluble residue in coal ash refers to the insoluble residue of coal ash measured according to the method described in JIS R5202 “Chemical chemical analysis method of cement”.

The coal ash has a brane specific surface area of preferably 2500 to 4000 cm ² / g, more preferably 2600 cm ² / g or more, further preferably 2700 cm ² / g or more, and even more preferably 2800 to 4000 cm ² / g. is there.
When the Blaine specific surface area of coal ash is large, the activity becomes high, and in a relatively early stage, the pozzolanic component (Al ₂ O ₃ , SiO ₂ ) contained in the coal ash is generated by the hydration reaction of Portland cement. It easily reacts with calcium oxide (Ca (OH) ₂ ). When the Blaine specific surface area of coal ash is 2500 to 4000 cm ² / g, coal ash and Portland cement can be mixed uniformly, and the chelating action of the trialkanolamine is a pozzolanic component in Portland cement and coal ash It reaches alumina (Al ₂ O ₃ ), and the pozzolanic reaction proceeds at a relatively early stage, so that the short-term strength development can be increased.
In this specification, the brane specific surface area of coal ash refers to a value measured according to JIS R5201 “Cement physical test method”.

Coal ash is contained in the mixed cement in an amount of 20 to 40% by mass and more preferably 25 to 35% by mass with respect to the total amount of coal ash and Portland cement. In the mixed cement, if the coal ash content is less than 20% by mass with respect to the total amount of coal ash and Portorado cement, the amount of coal ash is too small to effectively use the coal ash. . In the mixed cement, if the coal ash content exceeds 40% by mass with respect to the total amount of coal ash and Portorado cement, the amount of coal ash that has almost no hydraulic property in the short-term age is too much and mixed. The short-term strength development of cement decreases. The mixed cement contains 20 to 40% by mass of coal ash together with 100 to 300 mg / kg of the trialkanolamine with respect to the total amount of coal ash and Portland cement, and the coal ash has an SiO ₂ content of 55. When the mass ratio of 60 wt% and _SiO 2 / _Al 2 _{O 3} is one of 2.3 to 2.7, it is possible to contribute to improvement of the short-term strength development.

[Portland cement]
The type of Portland cement contained in the mixed cement is not particularly limited. Examples of Portland cement include ordinary Portland cement, early-strength Portland cement, moderately hot Portland cement, and low heat Portland cement.

  The mixed cement contains 60 to 80% by mass of Portland cement and preferably 65 to 75% by mass with respect to the total amount of coal ash and Portland cement. When the content of Portland cement is less than 60% by mass with respect to the total amount of coal ash and Portland cement, a hardened product having a desired strength cannot be obtained because the amount of cement is small. If the content exceeds 80% by mass, the amount of coal ash contained in the mixed cement decreases, and the coal ash cannot be used effectively.

[Trialkanolamine]
The mixed cement contains 100 to 300 mg / kg of a trialkanolamine having 3 linear alkanol groups having 3 or less carbon atoms with respect to the total amount of coal ash and Portland cement, preferably 150 to 250 mg / kg. is there. In the trialkanolamine, the hydration reaction of Portland cement is promoted by chelating action against Portland cement, and calcium hydroxide (Ca (OH) ₂ ) is generated at a relatively early stage. Is also assumed to extend to alumina (Al ₂ O ₃ ), which is a pozzolanic component in coal ash, and calcium hydroxide (Ca (OH) ₂ ) generated by the hydration action of Portland cement and pozzolanic component in coal ash ( Al ₂ O ₃ , SiO ₂ ) are more likely to react, and the pozzolanic reaction proceeds at a relatively early stage, which can contribute to short-term strength development. When the content of the trialkanolamine is less than 100 mg / kg with respect to the total amount of coal ash and Portland cement, there is too little chelating action of the trialkanolamine, and the hydration reaction of Portland cement becomes slow, There are cases where the short-term strength development cannot be increased. Even if the content of trialkanolamine exceeds 300 mg / kg with respect to the total amount of coal ash and Portland cement, the chelating action commensurate with the content does not occur and the hydration reaction of Portland cement cannot be further promoted. .

Trialkanolamine has three linear alkanol groups having 3 or less carbon atoms, and specific examples thereof include trimethanolamine, triethanolamine, and tripropanolamine. Of these, triethanolamine is preferable. For Portland cement that does not contain coal ash, triisopropanolamine and triethanolamine may have higher short-term strength (for example, mortar strength) when using triisopropanolamine, for example. .
On the other hand, in the case of a mixed cement containing 20 to 40% by mass of coal ash, the effect of promoting strength in a short period is greater when triethanolamine is used than when triisopropanolamine is used. When triethanolamine is used, the mechanism by which the contribution to the improvement of short-term strength development of the mixed cement containing coal ash becomes large is not clear, but the pozzolanic component (Al ₂ O ₃ , It is thought that calcium hydroxide (Ca (OH) ₂ ) is generated by promoting the hydration reaction of Portland cement by the moderate chelating action of triethanolamine at a rate at which reaction with SiO ₂ ) is likely to occur. .

[Production of mixed cement]
The mixed cement is ₂₀ % of coal ash having a SiO ₂ content of 55 to 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3 to 2.7 with respect to the total amount of coal ash and Portland cement. Manufactured by mixing -40 mass% and 60-80 mass% of Portland cement, and further mixing 100-300 mg / kg of trialkanolamine having 3 linear alkanol groups having 3 or less carbon atoms. can do.

  The mixed cement can be used as a mixed cement composition by blending an admixture in addition to coal ash and Portland cement. Examples of the admixture include blast furnace slag powder, limestone powder, quartz powder, gypsum and the like.

  EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited at all by these Examples.

Analysis of coal ash The coal ash of Examples 1-9 was analyzed. The analysis of the chemical components of coal ash was performed according to JIS R5204 “Method for fluorescent X-ray analysis of cement”. From the results of analysis of the chemical components of coal ash, the total value of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) contained in the coal ash and the mass ratio of silica to alumina (SiO ₂ / Al ₂ O ₃ ) Calculated.
Boron (B) and fluorine (F) in the coal ash of Examples 1 to 9 were measured according to the Cement Association Standard Test Method (JCAS I-53).
Further, the loss on ignition (ig.loss) and insoluble residue (insol) in coal ash refer to the insoluble residue of coal ash measured according to JIS R5202 “Chemical chemical analysis method”. Moreover, the brane specific surface area of coal ash was measured according to JIS R5201 “Physical test method for cement”. The results are shown in Table 1.

Moreover, when the amorphous phase of each coal ash was measured with the method mentioned later, the amount of amorphous phases of the coal ash of Examples 1-6 was the range of 66.7-68.2 mass%. The amount of amorphous phase of the coal ash of Examples 7 to 9 was in the range of 60.5 to 61.9% by mass. Table 1 shows the amount of amorphous phase (mass%) in each coal ash of Examples 1-9. The amount of amorphous phase _GFA (mass%) in coal ash in Table 1 is calculated from the amount of amorphous phase G _total (mass%) of coal ash by Rietveld analysis and the amount of unburned carbon (mass of mass) of coal ash. %) Is subtracted. A method for measuring the amount of crystalline phase and amorphous phase (mass%) in coal ash is described below.

(Measurement of crystalline phase and amorphous phase amount (mass%) in coal ash)
The amount of crystalline phase and amorphous phase (mass%) in coal ash was measured by a Rietveld analysis method using an internal standard substance with a powder X-ray diffractometer. As the powder X-ray diffractometer, D8 Advance (manufactured by Bruker AXS) was used. Measurement conditions, internal standard substances, and Rietveld analysis conditions are described below.
Measurement conditions X-ray tube: Cu
Tube voltage: 40 kV
Tube current: 40 mA
Measurement range of diffraction angle 2θ: start angle 5 °, end angle 70 ° / 75 °
* When rutile type titanium dioxide is added as an internal standard substance, if the end angle is 70 °, the peak shape of titanium dioxide around 70 ° cannot be obtained correctly. Therefore, the end angle of the sample added with titanium dioxide was set to 75 °.
Step width: 0.025 ° / step
Counting time: 60 sec. / Step
Internal standard: Rutile type titanium dioxide Rietveld analysis conditions Rietveld analysis software: TOPAS Ver. 4.2 (Bruker AXS)
Zero point correction: None Sample surface height correction: Yes Analysis target minerals: Quartz, mullite (3: 2), anhydrous gypsum, limestone, magnetite, hematite, titanium dioxide (only samples added as internal standard substances)
Selective orientation function of hematite phase: Selective orientation of hematite phase is assumed to occur in the diffraction line of (110) plane near diffraction angle 2θ = 35.5 °, and the initial value of the coefficient is set to 1 using the March Dollase function. Was made. For the magnetite phase, no preferential orientation occurred.

The procedure for measuring the crystalline phase and the amorphous phase of magnetite and hematite in coal ash is described below.
(I) As an internal standard, coal ash (sample 1) to which 20% by mass of rutile type titanium dioxide was added and coal ash (sample 2) to which no internal standard substance was added were prepared.
(Ii) Coal ash (sample 2) to which no internal standard substance was added was measured using a powder X-ray diffractometer, and the obtained powder ash (sample 2) powder X-ray diffraction pattern and the target mineral quartz , Mullite, anhydrous gypsum, limestone, magnetite, and hematite, and fitting each theoretical profile, quantitative analysis of each mineral to be analyzed contained in coal ash, the amount of each mineral (% by mass) ) Was calculated. For magnetite and hematite, the amount (mass%) of magnetite and hematite in the coal ash was calculated only from the coal ash (sample 2) to which no internal standard substance was added.
Sample 2 to which no internal standard substance is added is used for the quantitative analysis of magnetite and hematite. The diffraction angle 2θ of magnetite and hematite is a peak around 35.5 ° to 35.6 °, and the diffraction angle 2θ of rutile titanium dioxide. This is because the peak near 36.1 ° is close. In particular, when rutile type titanium dioxide having a small particle size and a small crystallite size is used as an internal standard substance, peak broadening occurs, and the rutile type titanium dioxide has a diffraction angle near 2θ = 36.1 ° near the bottom of the peak. However, when the content of magnetite or hematite overlaps (overlap), particularly when the content of magnetite or hematite is small, the quantitative value is greatly affected.
(Iii) Coal ash (sample 1) added with rutile titanium dioxide, which is an internal standard substance, was measured using a powder X-ray diffractometer, and a powder X-ray diffraction pattern of the obtained coal ash (sample 1) Analytical minerals such as quartz, mullite, anhydrous gypsum, limestone, hematite, magnetite, and titanium dioxide were fitted to each theoretical profile, and each of the minerals included in the coal ash (sample 1) with the internal standard added. Quantitative analysis was performed, and the amount (% by mass) of each analysis target mineral was calculated by analysis software.
(Iv) From the quantitative value of the rutile titanium dioxide of Sample 1, the total amorphous phase amount G _total (% by mass) containing unburned carbon was calculated by the following equation (A).
Total amorphous phase amount G _total = 100 × (Y−X) / {Y × (100−X) / 100} (A)
However, in Formula (A), X is the addition amount (20 mass%) of an internal standard substance, Y is the Rietveld analysis value (%) of rutile type dioxide.
(V) After quantifying the total amorphous phase from the content (mass%) of the crystal phase of the mineral to be analyzed of sample 1, the following (B) is obtained from the content (mass%) of the mineral to be analyzed of sample 2. The crystal phase content in which the total amorphous phase is taken into account by the formula is calculated (crystal phase (considering _total amorphous phase amount G _total )) = crystal phase (sample 2 analysis value) × (100−G _total ) / 100 (B)
However, in the formula (B), G _total is the analysis value of the sample 1 and the total amorphous quantitative value (%) obtained from the formula (A).
(Vi) The value obtained by subtracting the unburned carbon content (mass%) in the coal ash from the _total amorphous phase amount G _total (mass%) calculated from the formula (A) by the following formula (1) The amount of amorphous phase in the medium was G _FA (mass%). The amount of unburned carbon was determined by the ignition loss measured according to JIS A6201 “Fly Ash for Concrete” as the unburned carbon content (mass%) in coal ash.
Amorphous phase amount G _{FA in} coal ash (mass%) = total amorphous phase quantity G _total (mass%) by Rietveld analysis−unburned carbon content (mass%) (1)

The mass ratio of the amount of iron in the crystal phase contained in the coal ash to the amount of iron in the coal ash of Examples 1 to 9 (the amount of Fe in the crystal phase / the amount of Fe in the coal ash) was calculated as follows.
(i) The amount of Fe in coal ash is a measured value 1 of the iron content in terms of oxide (iron (III) oxide: Fe ₂ O ₃ ) measured in accordance with JIS R5204 “Method for X-ray fluorescence analysis of cement” From the following formula (2), the iron content was converted and calculated.
Iron content in coal ash (Fe content in coal ash) = Measured value 1 × 2 Fe / Fe ₂ O ₃ (111.6 / 159.7) (mass%) (2)
(ii) The amount of iron in the crystalline phase contained in the coal ash is the hematite in the crystalline phase calculated in consideration of the _total amount of amorphous phase G _total (% by mass) containing unburned carbon contained in the coal ash. The content (mass%) of the magnetite in the crystal phase calculated taking the _total amorphous phase quantity G _total (mass%) including unburned carbon into account, with the content (mass%) of The measured value 3 was calculated by the following formula (3).
Iron amount (Fe amount) in crystal phase considering _total amorphous phase amount G _total including unburned carbon contained in coal ash = [measured value 2 × {2Fe / Fe ₂ O ₃ (111.6 / 159 .7)}] + [measured value 3 × {3Fe / Fe ₃ O ₄ (167.4 / 231.5)}] (3)
(Iii) Total amount of amorphous phase including the amount of iron in coal ash (Fe amount in coal ash) determined by the above formula (2) and unburned carbon contained in the coal ash determined by the above formula (3) From the amount of iron in the crystalline phase considering G _total (the amount of Fe in the crystalline phase), the amount of Fe in the crystalline phase considering the _total amount of amorphous phase G _total including unburned carbon relative to the amount of Fe in coal ash The mass ratio (the amount of Fe in the crystal phase / the amount of Fe in coal ash) was determined. The results are shown in Tables 1 and 2.

(Examples 1-8 and Comparative Examples 1-6)
Ordinary Portland cement, Examples 1 to 9, and a mixture shown in Table 2 using a kind of additive selected from the group consisting of triethanolamine (TEA), triisopropanolamine (TIPA) and diethylene glycol (DEG). Cement was produced. The content of coal ash is a mixing ratio with respect to 100% by mass of the total amount of coal ash and ordinary Portland cement. Moreover, the addition amount of one kind of additive selected from triethanolamine (TEA), triisopropanolamine (TIPA) and diethylene glycol (DEG) is the addition amount (mg / kg) with respect to the total amount of 1000 kg of coal ash and ordinary Portland cement. It is. Table 2 shows the amount of chemical components (mass%) of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) and the mass ratio of silica to alumina (SiO ₂ / Al ₂ O ₃ ) for coal ash used in the mixed cement. ), Fe ₂ O ₃ chemical component amount (mass%), mass ratio of Fe amount in crystal phase / Fe amount in coal ash considering _total amorphous phase amount G _total including unburned carbon, Blaine specific surface area ( cm ² / g).

Mortar Strength For the mixed cements of Examples 1 to 8 and Comparative Examples 1 to 6, the mortar compressive strength at 3 days of age (in accordance with “11 Strength Test” in JIS R5201 “Physical Test Method for Cement” ( N / mm ² ). The mortar compressive strength of the mortar specimen using the mixed cement having a coal ash content of Comparative Example 6 of 25% by mass was set to 1.00, and Examples 1 to 8 and Comparative Examples 1 to 6 were used. The relative value of mortar strength was calculated.
Further, for some examples and comparative examples, the mortar compressive strength (N / day) of 28-day or 91-day age was determined in accordance with “11 Strength Test” in JIS R5201 “Physical Test Method for Cement”. mm ² ), relative to the mortar strengths of Examples 6 to 8 and Comparative Example 3, assuming that the mortar compression strength of the 28-day age of the mortar specimen using the mixed cement of Comparative Example 6 is 1.00 The value was calculated. Moreover, the relative value of the mortar strength of Examples 6-8 and Comparative Example 3 was calculated by setting the mortar compressive strength of the mortar specimen using the mixed cement of Comparative Example 6 to 1.00 as 1.00. The results are shown in Table 2.

As shown in Table 2, Example 1 having a coal ash content of 25% by mass with a SiO ₂ content of 55-60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3-2.7. In the mixed cements of -6, the relative value of the mortar strength at 3 days of age with respect to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg) is 1.14 or more, respectively, and short-term strength The expression was improved.
Further, SiO ₂ content of 55-60 wt% and the coal ash content weight ratio is 2.3 to 2.7 of _SiO 2 / _Al 2 _{O 3} is 30% by weight of the mixed cement of Examples 1 to 6 The relative value of the mortar strength at 3 days of age relative to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg) was 1.06 or more, respectively, and short-term strength development was improved. I was able to confirm.
The mixed cements of Examples 1 to 6 having a coal ash content of 35% by mass with a SiO ₂ content of 55 to 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3 to 2.7, The relative values of the mortar strength at the age of 3 days relative to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg) were 0.98 or more, respectively, and short-term strength development was improved.
Moreover, all the mixed cements of Examples 6 to 8 having a coal ash content of 25% by mass have a mortar strength of 28-day age relative to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg). The relative value and the relative value of the mortar strength of the 91-day age were 1.15 or more, and the coal ash contained in the mixed cement maintained characteristics that contribute to long-term strength development.

Further, the SiO ₂ content and the mass ratio of SiO ₂ / Al ₂ O ₃ satisfy the above range, include 200 mg / kg of triethanolamine (TEA), and consider the _total amorphous phase amount G _total including unburned carbon. The mixed cements of Examples 1 to 8 using coal ash having a mass ratio of Fe amount in crystal phase / Fe amount in coal ash in the range of 0.10 to 0.17 have a coal ash content of 25 mass. %, 30% by mass, and 35% by mass, the relative value of the mortar strength at 3 days relative to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg) is Comparative Example 1. The content of coal ash in the mixed cement of ˜5 was larger than the relative values of 25 mass%, 30 mass%, and 35 mass%, and the short-term strength development was improved. As shown in Table 1, an example in which the mass ratio of Fe amount in crystal phase / Fe amount in coal ash in consideration of _total amorphous phase amount G _total including unburned carbon is in the range of 0.10 to 0.17. Examples 1 to 6 have a mass ratio of Fe amount in crystal phase / Fe amount in coal ash exceeding 0.17 considering the _total amorphous phase amount G _total including unburned carbon. amorphous phase amount G _FA in the coal ash was often compared to the coal ash.

On the other hand, as shown in Table 2, Comparative Examples 1 to 2 using coal ash having a SiO ₂ content exceeding 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio exceeding 2.7. The mixed cement of No. 3 is a three-day material for Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg) in any case where the coal ash content is 25% by mass, 30% by mass, and 35% by mass. The relative values of the mortar strength of the ages were as low as less than 1.14, less than 1.06, and less than 0.98, respectively, and short-term strength development was not improved as compared with the mixed cements of Examples 1-6.
Further, the mixed cement of Comparative Example 3 having a coal ash content of 25% by mass has a relative value of the mortar strength at 28 days of age and 91 relative to Comparative Example 6 (coal ash content of 25% by mass, additive 0 mg / kg). The relative value of the mortar strength of the day age is 1.09, and the coal ash contained in the mixed cement also maintains the characteristics contributing to the long-term strength development, but compared with Examples 6-8 The long-term strength development was slightly lower.

As shown in Comparative Examples 4 and 5 in Table 2, when coal ash having a SiO ₂ content of 55 to 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3 to 2.7 is used. Even so, when triisopropanolamine (TIPA) or diethylene glycol (DEG) is used as an additive, the chelating action of the additive on ordinary Portland cement is not appropriate, and the mixed cements of Comparative Examples 4 and 5 are In all cases where the coal ash content is 25% by mass, 30% by mass, and 35% by mass, the mortar strength of the 3-day age relative to Comparative Example 6 (coal ash content 25% by mass, additive 0 mg / kg) Are less than 1.14, less than 1.06, and less than 0.98, respectively, and the short-term strength development was not improved as compared with the mixed cements of Examples 1-6.

As shown in Comparative Example 6 of Table 2, the case where coal ash having a SiO ₂ content of 55 to 60% by mass and a SiO ₂ / Al ₂ O ₃ mass ratio of 2.3 to 2.7 was used. However, when the additive is not used, as the coal ash content increases to 25 mass%, 30 mass%, and 35 mass%, Comparative Example 6 (coal ash content 25 mass%, additive 0 mg / The relative value of 3-day age mortar strength relative to kg) decreased. Since the coal ash itself has almost no hydraulic property in the short-term age, it is presumed that the relative value of the mortar strength of the 3-day age became lower as the coal ash increased.

  According to the present invention, coal ash whose generation amount is increasing can be effectively used with the increase in power generation amount at a coal-fired power plant, and coal having a specific component with high short-term strength development. Mixed cement containing ash can be provided.

Claims (6)

The total amount of coal ash and Portland cement, 20 to 40 mass coal ash SiO ₂ content of 55-60 wt% and the weight ratio of _SiO 2 / _Al 2 _{O 3} is 2.3 to 2.7 %, Portland cement 60-80% by mass and triethanolamine 100-300 mg / kg , the mass ratio of the iron content in the crystals contained in the coal ash to the iron content in the coal ash (crystal A mixed cement having an amount of Fe in the phase / Fe amount in the coal ash) of 0.10 to 0.17 . The total content of SiO ₂ and _Al 2 _{O 3} content in coal ash is 75 to 86 wt%, mixed cement according to claim 1. The coal _Fe 2 _{O 3} content in the ash is 5.0 to 8.0 mass%, mixed cement according to claim 1 or 2. The mixed cement according to any one of claims 1 to 3, wherein an insoluble residue (insol) content in the coal ash is 75 to 87 mass%. Blaine specific surface area of the coal ash is 2500~4000cm ² / g, mixed cement according to any one of claims 1-4. The mixed cement according to any one of claims 1 to 5, comprising 25 to 35 mass% of the coal ash and 65 to 75 mass% of Portland cement.